show effective model in agent comment/review footers (#618)

`toolState.model` was set only to `payload.model` (the stored slug, often
undefined for router/oss runs that derive the target from `proxyModel`).
the footer's "Using `…`" segment is gated on a truthy model, so router
runs on repos without an explicit model setting shipped reviews/comments
with no model badge — e.g. PR #614's review showed no model despite
running `openrouter/anthropic/claude-opus-4.7` via proxy.

now mirror the priority used by `resolveModelForLog` and `isGeminiRouted`:
`payload.proxyModel ?? resolvedModel ?? payload.model`. also reverse-look
up by `resolve`/`openRouterResolve` in `formatModelLabel` so a proxy
target like "openrouter/anthropic/claude-opus-4.7" still renders as
"Claude Opus".

main.ts

@@ -578,6 +578,12 @@ export async function main(): Promise<MainResult> {
     const resolvedModel = payload.proxyModel ? undefined : resolveModel({ slug: payload.model });
     const agent = resolveAgent({ model: resolvedModel });
 
+    // surface the effective model in comment/review footers. payload.model is
+    // just the stored slug (often undefined for router/oss runs that derive
+    // the target from proxyModel). matching priority with resolveModelForLog
+    // so the "Using `…`" badge reflects what actually ran.
+    toolState.model = payload.proxyModel ?? resolvedModel ?? payload.model;
+
     validateAgentApiKey({
       agent,
       model: payload.proxyModel ?? resolvedModel ?? payload.model,